Leaking via Backflow Preventer

I have a Bradford White MIITW75T6EN12 water heater that has recently started leaking cold water out of the backflow preventer. I felt both the pressure release pipe and the backflow pipe, only the backflow was wet.

Back in winter we had a mixing valve installed so we could supply hotter water to the basement radiant heat system but still keep temperatures at 120 for the kitchen sink.

First image is from the side at the blackflow preventer, second is the mixing valve installation. On the side is an Amtrol Term X-Trol ST5 expansion tank. Home was built in 2002 and we purchased Fall 08.

No changes or adjustments have been made since the mixing valve was installed and temperature on the heater turned up. This leak started about a week ago, I'm down in the basement at least 5 times a week for excercise and walk by the heater and softener each time to get to the "gym"

What you have there is a Duel Check with intermediate atmospheric vent. Watts makes one called a 9D.

If you are getting continuous discharge from it, it is an indication that the internal seating parts and surfaces may need to be cleaned. If its just intermittent discharge it can be caused by water pressure fluctuations. If what you have there is a Watts Â¾" 9D here is Watts's repair kit part number 0886010 it includes diaphragm assembly, disc assembly, seat, seat O-ring and two union seals.

I am just wondering what State do you live in. In Illinois there is not supposed to be a shut off valve between the expansion tank and the water heater. To correctly remedy that issue, is to remove the ball valve before the tank and the one after the tee heading back to the heater and install one ball valve before the tee on the recirculation line. If you ever need to change the tank, you just shut off the supply ball valve and the recirculation ball valve to isolate the tank. Also I would of installed the tee the tank is on pointing up to make changing the tank easer.

A properly sized and approved expansion tank shall be located on the outlet side of the check valve in the water heater's cold water supply with no shut-off valve between the heater and expansion tank.
​

I live in Grand Rapids MI. Are the shut off valves a problem itself or only when someone shuts off the flow to the expansion tank?

It hasnt dripped in the past 30 minutes, so it must be pressure related. The only other water related thing I can think of is having our sprinklers turned on recently. I've never noticed it leak during our use since the fall (we moved in after the sprinkers were already shut off)

Is this repair for the novice? My plumbing history consists of fetching a ring out of the U shape catch under the sink.

The shut off valves are not a huge issue. Just here in Illinois its a code thing.

The repair is pretty easy, you shut off the water to the water heater and from the recirculation pump, unscrew the unions that are holding the 9D-M2 in place and open it up and replace all the parts with the parts in the kit and reinstall.

If it never leaked in the past with the sprinkler systems being on, and it is now, its time to open it up. Watts also recommends that the strainer inside the unit be cleaned every six months. Here is the PDF for your unit. Scroll to page 2 http://www.watts.com/pdf/1910237.pdf

OK actually perhaps a silly question. I see there is a shut off valve to stop the input water from entering the tank above the backflow preventor (yellow handle in the picture on the right) and the black one going towards the pump.

Do I have to worry about water coming up towards the backflow from the heater tank? Like, should I turn off the water heater and let it cool for a while or is the pressure not that much and all that will come out is the water currently around the backflow unions?

I can think of a lot of places to put that backflow preventer, especially that one, (one of them being a place not mentionable in polite company), but the inlet to the heater would definitely NOT BE ONE OF THEM. It will discharge EVERY TIME the incoming pressure drops, such as the irrigation system starting.

I can think of a lot of places to put that backflow preventer, especially that one, (one of them being a place not mentionable in polite company), but the inlet to the heater would definitely NOT BE ONE OF THEM. It will discharge EVERY TIME the incoming pressure drops, such as the irrigation system starting.

Click to expand...

I know what you mean. I would of just put a swing check there since that is all needed. One thing that caught me a bit off guard though is why put a check valve there? Was it for the recirculation line? If so why not put the check valve on the recirculation line.